A typical field of application for generic interchangeable holder systems is their use in machines for preparing ground surfaces, more particularly in the field of road and way construction. These are frequently machines having a driven working drum which is mounted for rotation about a horizontal axis and on which a large number of ground preparation tools, more particularly cutters or chisels and more specifically round shaft chisels, are disposed. The entire block consisting of the working drum and the large number of ground preparation tools is also referred to below as the milling rotor. Such machines include, for example, so-called stabilizers, recyclers or road cutters, more particularly cold cutters. Under working conditions, the holders containing the cutting tools are exposed to high loads and to extremely high wear, caused, on the one hand by the broken ground material in the drum housing and, on the other hand, depending on the embodiment, by the round shaft chisel rotating, for example, in the chisel holder. The wear occurs, inter alia, particularly in the region of the bore accommodating the chisel shaft in the chisel holder and in the region of the contact surface of a possibly present wearing disk. Moreover, the chisel holder is worn out or destroyed in the case of fracture, loss, or wear of the chisel. In order to make it possible to replace the worn or broken components of the chisel holder easily and quickly, the use of so-called interchangeable holder systems has become established.
The essential components of such an interchangeable holder system are a basic module and an interchangeable holder connected to the basic module and comprising a cutting tool. More specifically, the interchangeable holder may be integrally united with the cutting tool or alternatively comprise a suitable tool head, which is configured to accommodate a ground preparation tool, for example a chisel, more particularly a round shaft chisel. The basic module is rigidly attached to the cylindrical external surface of the milling drum, which is usually mounted on horizontal bearings extending at right angles to the direction of travel of an appropriate construction machine, for example by fixed welding of the basic module to the drum body. Thus the basic module is the link between the interchangeable holder system and the drum body. The basic module also serves to provide bearings for the interchangeable holder or is configured to accommodate the interchangeable holder and provide bearings therefor. Frequently, there is provided for this purpose an interchangeable holder head in the basic module, which head may be in the form of an insertion bore in the basic module, for example. The interchangeable holder may be reversibly mounted on the basic module and comprises for this purpose, for example, a suitable journal, which is pushed into the insertion bore for the purpose of mounting the interchangeable holder on the basic module. The interchangeable holder is then fixed in position on the basic module by means of a suitable securing device comprising, for example, threads, or bores for locking pins and/or screw bolts, etc. The interchangeable holder may further be at least partially conical in shape and is pushed, for mounting purposes, into an insertion bore provided in the basic module.
The cutting tool in the interchangeable holder may, on the one hand, be integrally united with the interchangeable holder, for example in the form of a cutter. On the other hand, the interchangeable holder may be configured for accommodation of an independent cutting tool and for providing bearings therefor. This is frequently the case, for example, when a chisel, especially a round shaft chisel, is used. An appropriate tool head is then provided on the interchangeable holder, for example a cylindrical chisel head in the form of a slot for round shaft chisels. Round shaft chisels are frequently mounted in the interchangeable holder for rotation about their cylinder axis and are secured against axial displacement by suitable locking means, as for example a locking sleeve.
The advantage of such an interchangeable holder system lies basically in the fact that in the case of a defective ground preparation tool and/or an interchangeable holder, it is possible to selectively replace the tool and/or the interchangeable holder without it being necessary, for this purpose, to elaborately break the fixed connection between the basic module and the drum body and then re-establish it.
Although generic interchangeable holder systems have basically proved to be successful, there is still room for improvement. For example, the known interchangeable holder systems are frequently of an extremely bulky nature, due, for example, to the method of supporting the interchangeable holder on the basic module. Particularly those embodiments in which the interchangeable holder is placed in position in an appropriate insertion bore in the basic module at least partially by means of, for example, one or more studs or the like, both the interchangeable holder and, more particularly, the basic module must be comparatively broad and heavy in order to satisfy stability requirements. On account of the massive construction, more particularly the overhanging holder width, increased power requirements must be satisfied during transportation of the material or during mixing operations. Thus, a correspondingly high driving power must be available when the machine is in action, which is inevitably accompanied by increased acquisition and operating costs. Furthermore, the separation of the interchangeable holder from the holder is frequently hampered by this system. More particularly, in a corrosive environment, such as prevails, for example, when certain binding agents are to be incorporated in the subsurface, corrosion frequently takes place to additionally bond the interchangeable holder to the holder. This is particularly problematic in the region of pin-and-socket connectors between the interchangeable holder and the holder. Moreover, the production of the hitherto known interchangeable holder systems is comparatively cost-intensive, since broad fitment tolerances exist, particularly between the basic module and the interchangeable holder, which make an extensive manufacturing process necessary. Finally, the joint between the basic module and the interchangeable holder is frequently difficult to access, so that here again there is room for improvement.